Polyolefins are commonly prepared by reacting olefin monomers in the presence of catalysts composed of a support and catalytic metals deposited on the surfaces of the support. For olefin polymerization, transition metals, and especially chromium, are known choices for the metal. A number of supports for such catalysts are known in the art. The choice of support has a significant impact on the properties of the polymer that is formed. Silica supports have primarily been used because they form highly active polymerization catalysts. Silica supports, however, are not optimum because they tend to permit formation of long-chain branching (“LCB”) in the polymers they produce.
Alumina supports are also known in the art for use in olefin polymerization, and are believed to reduce the amount of long-chain branching, but their activity is generally not as high as seen with silica supports with the same transition metals.
It is therefore desirable to have an olefin polymerization catalyst that is highly active and minimizes long chain branching. Despite the work that has been done in this area, there is a need for an olefin polymerization catalyst that minimizes long chain branching and produces high molecular weight polymers.